South East Asia has witnessed a rapid increase in unintended medical consequences associated with high-risk drug injection practices, including increases in the prevalence and incidence of viral pathogens prevalent in IDU populations such as HIV-1, HBV, and HCV. These trends raise grave concerns about the future spread of HIV infection in South East Asia and may portend the emergence of a self-sustaining epidemic in the region. Of particular concern, is the rapid increase in new infections among young, male heroin IDUs in Viet Nam. Structured as a unique type of collaboration between HIV researchers at NDRI and public health researchers and community-based physicians at Hanoi Medical University, this study has the dual goal of developing an epidemiological profile of injection-mediated risk among young male heroin users, while simultaneously advancing the technical capacity of researchers in Viet Nam to respond to the emerging HIV epidemic among IDUs. Specific aims of the proposed demonstration project include: [1] To develop an epidemiological typology of the physical settings, situational events, social groups, and economic exchanges, in which young men use opiate-based drugs, including opium, morphine-base, and heroin, as well as the knowledge, attitudes, and beliefs regarding HIV risk in the injection of these substances; [2] To describe variability in behavioral practices employed in the preparation and injection of heroin-based drug solutions, including local drug marketing patterns, drug-acquisition strategies, and drug-sharing practices that may facilitate transmission of blood-borne pathogens; [3] To describe individual, social, and economic correlates of injectors' apprenticeship into heroin injection, including the pedagogical processes in which IDUs learn to prepare and inject heroin, their rationale for initiating and maintaining injection as a mode of drug (heroin) administration, and the early social course of heroin dependence; [4] To describe the accumulation of unintended medical consequences associated with the onset of heroin injection, particularly HIV and other viral pathogens prevalent among IDU populations; and [5] To extend concepts and methods adapted from anthropological ethnography in conducting epidemiological research among "out-of-treatment" populations in the U.S., with the goal of enhancing the technical capacity of researchers in Viet Nam in identifying and monitoring emerging trends associated with drug abuse and HIV.